1. Field of the Invention
This invention relates to a method and an apparatus for producing emulsion in which dispersion liquid is dispersed to a fine particle size in disperse medium, and more particularly to a method and an apparatus for producing emulsion having an uniform distribution.
2. Discussion of the Related Art
In the conventional method and apparatus for producing the emulsion, disperse medium and dispersion liquid are mixed by a preferable rate as a preliminary emulsion which is agitated by an emulsifying means, e.g. a high-speed agitator (dissolver), a homogenizer, an inline-mixer or the like, so that the stable emulsion which is emulsified to more fine particle size is produced.
When the emulsifying is performed by the above apparatus, required shearing force for the emulsifying greatly varies between far from and near by an emulsifying blade, because a region which the shearing force affects is limited around the emulsifying blades. Accordingly, there was a problem that the distribution of the particle size in the dispersion liquid was too wide.
Hereupon, devices which perform the uniform distribution of the particle size in the dispersion liquid are disclosed, e.g. a producing device of the dispersion liquid in which the shearing force supplying to the emulsion is increased continuously or stepwisely (Japanese Patent Application Laid-Open No. 59-26129); or a device which rotates an inner tube in the double tubes and supplies a preliminarily vibrated liquid into the body, so that the device occurs a flat current toward the current direction of an uniform liquid (Japanese Patent Application Laid-Open No. 56-139122).
There is a colloid-mill as the representative device of the former emulsifying device. In this device, however, the width (depth) of the emulsifying chamber is narrow as compared with the diameter of the chamber, and the supply of the mixed liquid to the device and the position of the outlet are not paid attention. As a result, the region which is effected by the uniform shearing force becomes narrow. The coarse particles, therefore, not to become small are discharged, and the "short-pass" phenomenon occurs. Specifically, when the flux is increased, the phenomenon is remarkable and causes the average size of the particles to be large and the distribution of the particles to broaden, in which the coarse particles remain. Accordingly, there is a defect that the device should be operated by low flux in order to obtain the emulsion having a narrow distribution of the particle size.
Regarding the latter, the device is used for producing a dispersion liquid including the large particles in 500 .mu.m degree size. Generally, this device is not adapted to produce a fine particle dispersion liquid emulsion. Furthermore, the vortex of plane current between the inner cylinder and the outer cylinder causes the distribution of the shearing force to be uneven and the distribution of the particle size to broaden. Moreover, the supplying inlet and outlet of the liquid are disposed on the header at both sides of the double tubes. The liquid current, therefore, is apt to flow along the most short distance between the inlet and the outlet. In this case, namely, when the flux is increased, the short-pass phenomenon occurs and causes the distribution of the particles to broaden, in which the coarse particles remain.
With both conventional devices, there are defects that the distribution of the particles of the dispersion liquid broaden and a large quantity treatment cannot be performed.